I think it's less about coaches not making a difference, and more about fans ability to actually determine the difference a coach makes tends to be limited.
Hell, MacLean was runner up and winner of the Jack Adams, yet most here seem to have thought he was a terrible coach, Boucher took us to the ECF, and people think he was terrible. Do we think Babcock would have done better at the helm than either of those guys? Honestly, it's hard to say.
People thought that Maurice was a bad coach when he was with the leafs, Missed the playoffs in 13 out of 18 of his years as HC until the Jets turned things around a he's been in the playoffs 6 out of 7 years between two teams, with a WCF and trip the cup finals to his name.
From the outside looking in, it's not easy to evaluate a coach, thats all.